Fluorine-containing elastomers, particularly perfluoroelastomers mainly comprising a tetrafluoroethylene (TFE) unit are widely used as sealing materials, etc. to be used under harsh environment because of excellent chemical resistance, solvent resistance and heat resistance thereof.
However with advance in technologies, more rigorous demand for characteristics has been imposed, and in the fields of aviation and space industries, semiconductor manufacturing equipment and chemical plant, sealing property under high temperature environment of not less than 300° C. is demanded.
To cope with such a demand, attempts to improve heat resistance by using a specific crosslinking system have been proposed. One example is a disclosure of a curable composition comprising a fluorine-containing elastomer having a nitrile group introduced as a cure site and being subjected to crosslinking with a curing agent and an organic or inorganic ammonium salt (for example, refer to JP2001-504885A). The curable composition of JP2001-504885A has an effect of giving excellent thermal stability and chemical resistance when cured, but it is necessary to improve compression set of a cured article obtained by curing the curable composition.